The invention relates to a process for producing knitted fabrics, in particular seat covers, having integrated fasteners.
In the past, fasteners, such as those in the form of tubes or eyes, had to be sewn onto a preassembled seat cover in a separate sewing operation. Since the seat covers always had to be assembled, in other words, the individual pieces of the seat cover had to be sewn together, sewing the fasteners onto the underside of the seat cover in an additional step constituted a relatively insignificant amount of additional work.
Today, the technology for manufacturing automotive seat covers on flat-bed knitting machines is significantly more advanced, so that it is now possible to knit a quasi-three-dimensional seat cover without ever having to sew one part onto another. This means that conventional sewingxe2x80x94the assembly processxe2x80x94is eliminated altogether. Sewing on fasteners now proves to be an extremely time-consuming additional step that negates part of the time saved with the new knitting technology.
EP 361 855 A1 discloses a process in which tubular fasteners are sewn on in a single piece during manufacturing, in other words, when the seat cover is being knitted. The advantage of this approach is that the additional step of sewing the fasteners on at the desired locations is eliminated. However, this process greatly increases machine operating times, and the tubular fasteners, which are present in the form of tubular knitted pieces, cannot be produced in any desired length or any desired strength. Another disadvantage is that the locations at which the fasteners are knitted on are generally visible on the visible side of the seat cover.
The object of the present intention is therefore to create a process that permits seat covers having integrated fasteners to be manufactured quickly, and in which the fasteners exhibit a high degree of stability and are less visible from the visible side of the knitted fabric than is the case in prior-art processes.
In the invention, connecting pieces, loops, or tabs are integrated in the knitted fabric at the desired fastening locations while the knitted fabric is being produced. Said connecting pieces, loops, or tabs can either be knitted at the same time as the knitted fabric, or they can be knitted in as a premanufactured part when the knitted fabric is being manufactured. The connecting pieces, loops, or tabs are at least partially manufactured from a thermoplastic material, or a physically or chemically reactive material, in particular thread, whose shape can be altered by means of thermal, physical, or chemical treatment in order to form a fastener. A volume change, such as an increase in thickness, and/or an increase in the hardness of the area being treated can accompany this process. With the treatment, in particular the thermal treatment, the connecting piece or tabs can be formed using a separate premanufactured material that is also thermoplastic or physically or chemically reactive and that is connected to the knitted piece during the course of manufacturing. This element may preferably be supplied to the knitting area from a roll having a special feed system, such as a controllable feed system, via the thread guide rails on the flat-bed knitting machine and the needle gap. In the knitting area it is then knitted together with the knitted piece at the fastening points.
In addition, other elements such as metal strips, wires or eyes made of metal or plastic can be combined with the treated area. These elements can form the actual fastening points in the fasteners.
The connecting piece can be rolled up and heatedxe2x80x94for example in a thermal processxe2x80x94in such a way that a fastening welt is produced. This welt could then be pulled into a rail on a support for an automotive seat. During the thermal process, one or more eyes can be formed in the connecting piece and said eyes could then optionally be reinforced with metal rings, if desirable due to the presence of higher fastening forces. Rods or cords can subsequently be inserted into the eyes formed in this manner, or into loops formed after the treatment process, to produce the fasteners used to fasten the knitted fabric to the frame.
The thermoplastic material of the thread used to knit the connecting piece is preferably a material that is harder and preferably non-elastic after the thermal treatment process and is able to withstand higher forces. The connecting piece/loop/tab can also be reinforced in particular using materials from the family of fiber composites. Since materials and composites having properties that differ from those of the remaining knitted fabric can be used for the connecting pieces, the first rows of the connecting piece, for example, can be knitted using a thicker thread and can therefore form a bead that is already thicker before the thermal/physical/chemical treatment process is carried out.
The process of the invention can even be used to produce tubes as fasteners by folding over the connecting piece one time and then fusing it to another area of the connecting piece at the outer edge. During the fusion process, the entire connecting piece material can be fused together in such a way that the entire tube body is much more rigid than the originally knitted thread material. In this way, rigid and extremely stable fasteners that have virtually no elasticity can be produced, similar to those disclosed in the prior-art tubular knitted fabrics in the aforesaid European publication.
Integrally knitting a connecting piece onto a knitted fabric, such as seat cover, is an essentially known art. It can be accomplished by activating or deactivating certain areas of the needle bed, or by knitting the connecting piece on a second needle bed and transferring it onto the main knitting bed at the desired location, so that the said connecting piece becomes an integral part of the knitted fabric. Of course, the connecting piece does not need to be knitted from the same thread as the rest of the knitted fabric. Since this connecting piece has to be able to serve as a fastener and withstand relatively high forces following the thermal treatment, it can be knitted, for example, from a stronger thread. By properly selecting the thread material, it is possible to take into account the desired amount of deformation following the thermal posttreatment. One can therefore use a thread material adapted to a given application, regardless of the thread material used in the remainder of the knitted piece. The part of the connecting piece or tab that will not be treated thermally, physically, or chemically can also be knitted using a thread having a higher elasticity and/or a more elastic bond, thus permitting the fastener to be attached to a frame or to another fastener with an elastic preload.
Moreover, it is not necessary that the connecting piece be knitted at the same time as the rest of the knitted piece, and it may be thermally treated after it is joined to the knitted fabric. Thus, the connecting pieces can be knitted separately from the remaining knitted piece and be thermally treated ahead of time in order to form a fastener. In this case, the integration of the premanufactured fastener is accomplished merely by transferring the loops from the separate needle bed on which the loops of the connecting piece are engaged onto the needle bed on which at least one row of the knitted piece has been knitted.
In this regard, it must once again be noted that it is possible for the process of the invention to produce the entire knitted fabric, including the fasteners, on a flat-bed knitting machine or on a circular knitting machine. The thermal treatment to produce the fasteners can take place either before or after the connecting piece is connected to the knitted piece.
The process of the invention can be used on flat-bed knitting machines as well as on circular knitting machines. When stripers or sinkers are used with a plurality of needle beds, the connecting pieces as well as the knitted piece can easily be knitted in an alternating fashion or simultaneously.
The thermal treatment of the loops allows all manner of fastener shapes to be produced-for example, hooks facing in one direction, hooks facing in two directions, loops, welts, braiding, and many other configurations. In order to reinforce the fastening area, various materials made of metal, plastic, natural or inorganic fiber materials can be used. Following the thermal treatment, these materials are connected in an interlocking manner to the fiber materials of the connecting piece.
The material is preferably joined to a fastener or fastening profile during the thermal, physical, or chemical treatment. This fastener can possess the preformed fastening areas or fastening profiles in order to fasten the knitted fabric to the frame. During the treatment, all that needs to be done is to connect the connecting piece to this fastening profile. This is particularly easy to accomplish if the fastener or fastening profile is made of the same material as the thermoplastic or physically or chemically reactive material of the connecting piece or tab that is to be treated.
The invention is not just limited to fastening seat covers on seat cover frames. It can also be used to fasten pieces of trim (design) fabric, insulating parts, filter textiles, medical textiles, etc.